1995 Camaro Missing, Running Rough HELP

[91TransAmGTA]

So i picked up a 1995 Camaro z28 M6 with a blown head gasket cyl #7 Yanked the engine out and went through it all. New lifters, oil pump, timing chain, new summit racing opti spark, had heads rebuilt stock. put it all back together and it has a miss when given any throttle from idle. doesnt have power to even go 40 mph. it sounds like its missing hard. i have rechecked timing cam sprocket at 6 o clock and crank at 12 o clock. i have went through 4 optis with same results. new ICM new coil, new tr55ix ngk plugs, compression all around 200-210 psi
new tps sensor, deleted EGR, deleted evap purge solenoid, deleted air pump, new 24lb bosch injectors with conversion pigtails and had them flowed to reassure they were good. longtube headers, new o2 sensors offroad y pipe, not muffler its open at ypipe. i spray water onto headers after idling for a couple mins and all 8 headers tubes are scorching hot. rocker adjustment have been double checked but im not to worried about them since i have good compression. im at a loss here i dont know what to do. i bought a ALDL cable and i have winflash and tuner pro rt to datalog. i unplugged maf at idle and it made no difference. ive checked spark plug wires over and over and firing order is correct.

[Injuneer]

Have you checked the fuel pressure with the engine under load? Looking to maintain 42 PSI WOT.

Checked the valve adjustment? Have you checked engine vacuum at idle? Looking for 20”Hg with stock cam.

Didn’t see plug wires in list of replacements? Did you check plug gap before installing?

Has the MAF sensor been cleaned? No leaks in the rubber inlet elbow? Elbow is fully over the throttle body flange at the bottom?

Stock tune?

Checked it for codes?

I find Scan9495 to produce data logs in a useful format. Software is free:

https://www.camaroz28.com/forums/computer-diagnostics-tuning-36/scan9495-free-obd1-scan-app-93-94-95-lt1-874306/

Data log guide:

https://www.camaroz28.com/forums/computer-diagnostics-tuning-36/lt1-pcm-scanning-guide-886891/

[91TransAmGTA]

Yes fuel pressure is within spec. Valve Adjustment im checking as we type. I need to check engine vacuum. It has stock cam. Plug wires were replaced with OMNI brand from oreilly. Plug gap correct. Maf Sensor ive cleaned with maf cleaner. I smoked the intake and have a small tear on intake rubber elbow. no other intake leaks. Stock tune power wise i just flashed another 95 m6 tune this morning with vats and emissions all disabled etc. same result. i tried another 051 ecm with same result. got a .bin off interwebs for a stock 95 m6 car and flashed to 2nd ecm and same results. codes that were popping up were for egr, evap purge valve, 3-2 skip shift, fan 1 circuit. disabled those flags in the tune so no more ses light. i have a datalog file i took this morning at idle.

one thing ill tell you is this car is open at the off road y pipe so its extremely loud and sounds like this thing has a massive cam in it. its loping and shaking entire car. could that be a sign of overadjusted valves? causing overlap. also noticed this morning with my temp gun CYL #2 and Cyl #1 and relatively colder then the other 6 cylinders. ive swapped around injectors and put 2 new plugs in those 2 cylinders and same result. compression 2nd time was 220 on both cylinders

[Injuneer]

Did you check the cam dowel pin length? Unlikely you would receive 4 bad Opti's in a row, or that they would all be indexed incorrectly. But not unheard of for a short pin to slip out of the index hole in the Opti, and that could happen 4 times in a row. See first paragraph here:

http://shbox.com/ci/cam_install.html



And by fuel is “within spec” you are saying at WOT/heavy fuel demand? Not just tested at idle.

The hole in the inlet elbow is allowing air to bypass the MAF, screwing up the PCM's ability to control the A/F ratio, particularly under sudden throttle opening.

If you have a scan, the engine vacuum can be derived by subtracting “barometer” from “MAP”. If you live near sea level, barometric should read about 100 kPa (~30”Hg). Idle vacuum with stock cam will typically be about 30-35 kPa (10”Hg). 10” Hg minus 30”Hg = -20”Hg vacuum.

By open exhaust description, I assume stock manifolds, stock O2 sensors in stock location, and full Y-pipe is in place, with a straight pipe at the end in place of the cat.

[91TransAmGTA]

I didnt measure the cam dowel pin. But the opti wasnt forced on. It sat flush against mounting areas. When i removed old optis there was no sign of dowel pin coming out of place of optispark dowel pin slot. Ive tested fuel pressure at idle and WOT. no Fuel in vacuum line either. i have ordered a new intake rubber elbow on ebay. i have a manual vacuum gauge i can hook up. i have tons and tons of tools and specialty tools. i have longtube headers, with off road y pipe. no cats nothing. exhaust is open where y pipe ends.

[Injuneer]

If the cam dowel is too short, it doesn’t make it necessary for the Opti to be “forced on”. It will simply not completely engage the index hole in the Opti. I've seen it happen, and verified it with the diagnostic data from the crank position sensor. Did not determine the problem by looking at the Opti. Was doing it over the internet. There's a thread on this site where the problem was identified and turned out to be correct. But unfortunately, only the OBD-2 1996 and newer have the CKP for misfire detection.

I obviously can’t say with any certainty the dowel pin is your problem. It's just a problem I have seen in the past that you might want to consider. The timing errors should show up as weaker engine vacuum.

On the exhaust, just checking to make sure you weren’t somehow running open headers, which messes with the O2 sensors in the collectors.

[91TransAmGTA]

Okay so i found out my rockers were way overtighened. I loosed them all and re did the sequence following tdc pistons and valves closed. I found my passenger o2 sensor wire had been mysteriously cut by my starter developing a crack, and flexing against block and cut the wires. Got new starter and flywheel overnighted at oreillys. Going to pull transmission today and have it back together in the morning. Will report back. If nothing changes i will be sure to pull opti and measure cam dowel pin with my caliper. Thanks man! Thread will continue just got to fix these problems and see if anything changes.

[91TransAmGTA]

Okay so i got valved adjusted again, zero lash plus i did a 1/2 turn. Car still has same issue. But ive tried a different ecm and it helped nothing at all. Replaced intake boot and didnt help. One thing i didnt mention is i replaced the injectors with bosch IV 24 lb injectors with conversion pigtails. They were flow matched before shipped to me. Car sounds like it has a major cam at idle, but its stock. Havent measured vacuum yet though. Disconnecting the maf sensor while idling helps with a surge the car has but misfire is still there. Tomorrow afternoon im going to pull all the spark plugs and inspect them and also perform a compression test again.

[91TransAmGTA]

Also i forgot to mention like 2 days ago my cyl 1 & 2 headers pipes were way colder than the other 6 and today after adjusting valves, my cyl 1 & 2 were equally hot but now cyl 8 & 7 were cold just like 1&2 were before. This is weird. Brand new ngk tr55ix plugs and new wires like ive mentioned before

[91TransAmGTA]

Also my o2 are new and mounted right at the end of the longtube headers and im using o2 extensions pigtails for both banks. When i pulled transmission last night the headers inside were coated black likes its running super rich. My blm is at 112 at idle for both banks.

[Z28pr0jekt]

Random but double check the IAC valve in the throttle body, mine was stuck open with no spring tension left and caused the car to dump fuel and want to stall when I was coming to a stop. Datalog read like the IAC was working but it wasn't. Have you pulled the plugs and checked how some of them look (i.e. black?)

[91TransAmGTA]

data log shows iac fine but ill pull it and check it. It does want to idle around like 1100-1200 and wont come down.

[91TransAmGTA]

Engine vacuum is at 10 in hg

[rentedmule]

Have you tried shutting off all the lights and looking under the hood while it's running? Maybe the new plug wires are defective and arcing off something. Probably not, given the description of changing cold header tubes, but maybe worth a look.

[91TransAmGTA]

Have you tried shutting off all the lights and looking under the hood while it's running? Maybe the new plug wires are defective and arcing off something. Probably not, given the description of changing cold header tubes, but maybe worth a look.

Ill give that a try tonight. would that make the car sound like it has an aggressive cam?

[91TransAmGTA]

https://youtube.com/shorts/j_ATlGVqc9s?feature=share
gotta click on above link for another video



https://youtu.be/AXQu_gpgCVM

check this out

[Z28pr0jekt]

Geez the beginning of that video reminded me of my CC306 cam.

[91TransAmGTA]

Im about to flash a random 1995 CC306 tune i found off internet and see if car responds better.

[91TransAmGTA]

no change with cc306 tune

[Z28pr0jekt]

Did you get a chance to pull the IAC? Do you have a wideband sensor or pull plugs to see what they look like?

Also, I know you checked the temp at the headers and this is a pain to do on an LT1 but while the car is running, I would 1 by 1 pull a plug wire off and see if that changes the idle at all. This is likely common sense but if you pull a wire and nothing changes, that cylinder is likely not getting spark.